The present invention relates to a printer, particularly to a matrix printer in which needles or styli are provided as print elements and including a platen mounted in a frame of the printer, and more particularly the invention relates to the construction of such a platen in a printer which attenuates the development of noise both in the ambient air and as propagating in and emerging from various metallic parts themselves.
Printers of the type to which the invention pertains are usually provided for on line operation and in conjunction with a particular input facilities, establishing immediately and directly the subject matter that is to be printed. Simply for reasons of the environment in which they are used, these printers should not be too noisy. Take a simple word processing facility or a ticket printer or other public or private (but not unmanned) situations. The noise, developed by a printer, is usually attributable (primary source) to the impact of the print needles, both during printing, as well as retraction, of such a needle. There is a direct relationship between impact strength and print speed. Moreover, the parts in question are to be made quite strong simply to impart a long use life upon the equipment, but that, in turn, contributes further to the noise level produced by these parts whenever impacting. In addition, a strong print action is required because in many instances not only an original but also a number of copies, for example, five copies, are to be printed simultaneously. This is, for example, the case in document printing, ticket printing or the like.
In investigating the matter, it was found that noise is not only produced by the print styli themselves as impacting upon the print medium, the platen being underneath but also by and in metal parts serving as platen. The vibrations set up and propagating in the platen will usually propagate into the print frame and the housing as a whole, and for reasons of unforeseeable resonance conditions secondary vibrations may be set up.
A printer of the type to which the invention pertains is, for example, shown in German Patent No. 29 28 233. This patent, moreover, is directed towards reducing the noise development. Herein then, the print platen is mounted in noise attenuating mounts made of rubber; this way some attenuation that is developed does indeed obtain. In addition, a certain attenuating weight are provided which is fastened by means of screws to the upper and lower sides of the platen, there being interposed an attenuating foil made of rubber. Such additional weights, however, are very little effective because, for example, shock waves introduced into the platen, propagate, in fact, nearly horizontally, but the particular arrangement of attenuating weights and attenuating foils do in fact very little to attenuate these vibrations.